1. Field of the Invention
The invention relates to a milling machine for milling and turning rod material into individual workpieces.
2. Discussion of Related Art
Various machine tools for milling and drilling workpieces are known. The principal advantage of these machines is that the workpieces can remain on the same table and in one setting for different milling and drilling operations. As a result, machining accuracy is increased and the overall sequence of operations is simplified, since the number of clamping operations is reduced.
One type of such machine tool is related to turning machines due to its basic concept, and is applicable to workpieces which are mainly processed by turning operations. For accomplishing special isolated milling operations, spindle heads may be provided as auxiliary devices at appropriate locations in these turning machines.
Another type of machine tool for carrying out milling and turning operations on workpieces is based on the technical concept of milling machines, which differ from turning machines in having a greater number of shifting axes. These machines comprise a spindle head with an integrated tool spindle, which is typical for milling machines. It is mounted on a column so as to be shiftable along one or more coordinate axes by means of a motor. A clamping device is provided on a workpiece table, which comprises a workpiece holder for fixedly mounting usually rod-shaped workpieces of different sizes that are inserted into the workpiece holder from an adjacent rod magazine. In machine tools of this type, the milling operations outnumber the turning operations carried out on the same workpieces.
PCT publication 98/08648 shows a general milling machine for milling and turning rod material into individual workpieces. The machine has a machine bed and a mobile column shiftable along the two horizontal X and Y coordinate axes. On the vertical front side of the mobile column, a motor driven vertical slide carrying a spindle head, including a vertical work spindle, is guided so as to be movable along the vertical Z coordinate axis. On the machine bed a workpiece carrier having a clamping device, such as a draw-in collet or a multiple jaw chuck, as well as a rotary drive coupled therewith, is provided on a stationary table laterally adjacent to the workspace of the tool spindle. The clamping device defines a clamping axis along which the rod-shaped workpieces are fed in a step-wise manner. The clamping device can further be pivoted about an axis extending transversely with respect to the clamping axis in two bearing blocks attached to the machine bed or the table. The table is formed as a turntable. The numerically controlled rotary drive can drive the workpiece holder with speeds suitable for turning operations. These speeds can be, for example, about 4000 rpm to about 6000 rpm. In this machine tool the workpiece end portions protruding from the workpiece holder into the workspace can be subjected to turning operations with the aid of the work spindle in the conventional way. To carry out milling operations, particularly at the end portions of the workpiece, in the same setting, the workpiece previously is separated from the rod material and fixed in the workpiece holder, and can be inclined by pivoting the workpiece holder so that even the workpiece end portions can be machined, for example rounded, with the aid of the vertical milling tool.
From European patent 0,368,996, a similar milling machine for carrying out milling and turning operations on a workpiece is shown, in which a vertical spindle head including a milling spindle is provided on a movable column so as to be movable along the vertical Z coordinate axis. A gripping and pivoting unit is located on a slide that can be independently shifted horizontally in the longitudinal direction of the machine column. It provides for clamping a rod portion, the front end of which has already been machined. With a pivoting movement of the gripping and pivoting unit about a horizontal axis the rear side of the workpiece may be machined from different directions by the vertical milling tool.
A turning and milling machine for machining workpieces of wood, plastic and metal having a vertical slide shiftable on the face of a stationary machine column along the vertical Z axis and having a spindle head mounted thereon, is shown in German patent publication 197 39 512. In front of the face of the column and laterally adjacent to the workspace of the vertical work spindle, a clamping device is provided which is turnable by means of a motor. The rod-shaped material to be machined into individual workpieces is mounted in the clamping device. The clamping axis of the clamping device extends along the horizontal X coordinate axis. However, milling the rod end portions protruding from the clamping device from all directions is not possible with this machine.
German patent publication 196 33 899 shows another machine tool for machining rod-shaped workpieces. It has a machining head adjustable in a plurality of coordinate axes for machining a free end portion of the workpiece, as well as a clamping device including an integrated retainer for the rod-shaped workpieces. The end portions of the workpieces can be machined from five sides by laterally pivoting the clamping element holding the respective workpiece. The machining head containing the horizontally oriented tool spindle may be adjustable on a rotatable turntable in three axes.
Finally, a universal machine tool for accomplishing milling and turning operations on larger workpieces is shown in German patent publication 199 18 082. This universal machine tool carries a slide that is movable on a bed extending to the front in a direction transverse to the front side of the movable column in the longitudinal direction of the bed. A rotatably driven, relatively large turntable is provided on the slide. On the front side of the shiftable column a vertically movable console is provided. The end face of the console is inclined downward at an angle of about 45xc2x0. A pivoting head with a work spindle is disposed on the end face of the console. With a rotation of the swivel head about the axis perpendicular to its bearing surface, the work spindle can be moved from a vertical operating posture into a horizontal posture, or vice versa.
It is one object of the invention to provide a milling machine for machining rod-shaped materials into individual workpieces. The machine has a simplified structure as compared to previous machines and it enables universal all-over milling and turning of the protruding rod end portions into individual workpieces.
According to the invention, the stated object is accomplished by mounting the spindle head on a horizontal slide so as to be pivotable about an axis perpendicular to the spindle axis. The motor-driven horizontal slide is movable on the stationary column along the X coordinate axis parallel to the clamping axis. The clamping device comprises a rotary drive of dimensions suitable for turning operations and is disposed on an inclined console located on the face of the column laterally adjacent to the workspace and is movable in guides along the vertical Z coordinate axis by means of a motor.
As the spindle head may be pivoted about its longitudinal axis, the spindle head may be fixed in pre-selected inclined postures so that a rotatably driven milling tool mounted in the tool spindle may, for example, produce transverse grooves or inclined bores in the protruding end portion of the workpiece. However, the spindle head can also carry out a predetermined pivoting movement during a machining operation, so that, for example, round or spherical surfaces may be formed at the end portion of the workpiece with the correspondingly selected milling tool. Likewise the possible inclined postures of the spindle head, and thus the work spindle, enable certain turning operations, for example, the production of undercuts, if a turning tool is mounted in the spindle and the workpiece disposed in the clamping device is rotated with the speed required for this operation by its rotary drive. The provision of the spindle head on a horizontal slide shiftable on the stationary column results in a sufficient number of shifting paths along the coordinate axis parallel to the workpiece axis. Thus, the workpieces may be machined with an inclined tool in all of the workspace, and the tool exchange of the milling and turning tools from at least one magazine may be carried out according to the pick-up principle in a simple manner and within relatively short periods of time. The inclined console is vertically movable along column guides and has the clamping device disposed on its top laterally displaced with respect to the vertical guides. The inclined console is functionally connected with the capability of tilting the tool. In this manner the workpiece holder is located directly adjacent to the work area so that the protruding end portions of the workpiece are securely fixed. On the other hand, the insertion end of the clamping device protrudes laterally beyond the machine column so that the rod-shaped material can be inserted into the clamping device in a simple manner, for example, from a rod magazine.
Advantageously, the magazine may be disposed and mounted to the column on the side of the workspace opposed to the clamping device. The predetermined tool exchange position is directly accessible with a movement of the spindle head on the column. The free space required for the provision of the tool magazine is ensured by the fact that the inclined console can only be vertically moved. The invention provides a machine tool with universal applicability and relatively small dimensions.
The universal applicability of the machine tool according to the invention is considerably enhanced by its table construction. This table is provided in front of the face of the column and below the workspace. It comprises at least one bolster plate on which an auxiliary element, for example a tailstock, a workpiece turning device, a measuring instrument or the like, may be mounted. This table construction together with its base is conveniently formed as an integral, highly rigid component which includes the inclined console carrying the clamping device and is movable in the vertical guides of the machine column. In one embodiment, the table construction is provided with a vertical front bolster plate, as well as a horizontal bolster plate, each having flutes in which different auxiliary devices may be selectively mounted.
The machine tool according to the invention incorporates the known advantages of a universal milling machine with those of a turning machine. The respectively required turning and milling tools may be automatically inserted into the multi-axially turntable work spindle within a few seconds. The machine tool according to the invention is particularly suitable for the production of shorter, more complex workpieces, including inclined or spherical surfaces, grooves, bores, or the like from rod-shaped materials having a relative large diameter. The milling operations should, however, outnumber the turning operations.